[PATCH 2/3] perf inject: Enter namespace when reading build-id

[Namhyung Kim <namhyung@kernel.org>]

It should be in a proper mnt namespace when accessing the file.

I think this had no problem since the build-id was actually read from
map__load() -> dso__load() already.  But I'd like to change it in the
following commit.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 tools/perf/builtin-inject.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
index 59576877c67f..a2804d906d2a 100644
--- a/tools/perf/builtin-inject.c
+++ b/tools/perf/builtin-inject.c
@@ -23,6 +23,7 @@
 #include "util/symbol.h"
 #include "util/synthetic-events.h"
 #include "util/thread.h"
+#include "util/namespaces.h"
 #include <linux/err.h>
 
 #include <subcmd/parse-options.h>
@@ -419,16 +420,19 @@ static int perf_event__repipe_tracing_data(struct perf_session *session,
 
 static int dso__read_build_id(struct dso *dso)
 {
+	struct nscookie nsc;
+
 	if (dso->has_build_id)
 		return 0;
 
+	nsinfo__mountns_enter(dso->nsinfo, &nsc);
 	if (filename__read_build_id(dso->long_name, dso->build_id,
 				    sizeof(dso->build_id)) > 0) {
 		dso->has_build_id = true;
-		return 0;
 	}
+	nsinfo__mountns_exit(&nsc);
 
-	return -1;
+	return dso->has_build_id ? 0 : -1;
 }
 
 static int dso__inject_build_id(struct dso *dso, struct perf_tool *tool,
-- 
2.28.0.618.gf4bc123cb7-goog